Clearly this is the divot where our mountain came from. It's the simplest possible explanation!

Thank you, these feature-centered animations are really useful.

Fortunately for us, golf etiquette wasn't followed in this case.

Regarding this rayed crater:

Click to view attachment

It seems to have exposed a pocket (or pockets) of the white stuff (spot #5 material):

Click to view attachment

Now are the rays (and bright material beyond the rim) some white stuff that has been thrown out during the impact, or are they conventional rays similar to those on the moon? The scarcity of rays on Ceres overall, along with the patchy albedo in the crater, make me think they are the white stuff.

Now since the crater likely formed millions of years ago, this might indicate the white stuff can lie exposed for long periods. I would think ice would be ruled out if this is the case.

Anorthosite buried under regolith, exposed in some cases by impacts (spot 5) or tossed out, as in this case? Very white stuff, like the Genesis rock?

Given our Lunar upbringing, yes, anorthosite was the first thought (think Aristarchus). But this is a strange new world. Wait a few weeks til we get the science cameras and some spectral signatures and this question will be answered in short order.

I'm leaning towards salt deposits around vent areas. FWIW.

--Bill

An attempt at a geologic map:

Click to view attachment

Legend:

White/magenta - Bright spots.
Green - Smooth scarps and broad valleys.
Blue - Narrow, fracture-like valleys.
Yellow - Smooth mountains. May be associated with smooth valleys/scarps.
Orange - Sharply-defined mountains.

Features may be added, changed or removed upon closer examination.

Provided the estimate of about 2.1 g/cm³ for Ceres' mean density, derived from the rotation period and the oblateness, turns out to be roughly correct, together with at least some gravitational differentiation, shouldn't the top-most surface layers consist mainly of water-solvable compounds, or at least of light reaction products with water?

Anorthosite (density about 2.7 g/cm³), if I understand it correctly, is mainly made of plagioclase feldspar, which should readily weather (p. 4f) in the presence of at least liquid water.

Another beautiful theory, destroyed by an ugly fact. Ah well. Okay, it almost certainly can't be anorthosite, given that the mineral is more dense than Ceres' bulk density, so no self-respecting anorthosite would be found near the surface. It could be some other bright bedrock mineral, I suppose, though I don't know what.

Or even a salt, though we'll have to see. There was recent news that sea salt turns brown under cosmic radiation exposure, in a very short period of time, with a claim that a similar material could be the brownish stuff on Europa's surface. So why's this stuff white, if it's salt? The longer we go without seeing any plumes, the less likely any endogenous deposition or volatile would seem to be, no? Makes me wonder more and more what the stuff is in the bottom of Sander on Mercury.

"So why's this stuff white, if it's salt?"
Besides halite ("rock salt") there exist several dozens of evaporitic minerals.
One of my favorites is kieserite, together with associated minerals (including halite or bassanite), formed from epsomite by loss of bound water.
But since there is a large number of options, I'm probably wrong. Salammoniac (also white) would be a great find.

A couple of domes, much easier to see in ZLD's animations.

Click to view attachment

In that image are also a row of "three sisters" toward the upper right and a small pimple (how I hate that perfectly descriptive word) toward the lower right (seemingly within the large crater edge and more rounded looking than other features in the area). And in the full gif, another rise seems occasionally visible to the right of the three-sisters feature. This region has many apparent rises--some very subtle.

Click to view attachment

A nice valley leading towards that mountain. This should look quite spectacular at a lower altitude.

Has enough imaging been completed to make reasonable conclusions based on crater size distribution?

I call this 'Catenae Galore':

http://solarsystem.nasa.gov/news/display.cfm?News_ID=49244

I call it 'Rock-Paper-Scissors' (smash.... cover.... cut).

Those aren't just shadows on the image-lower slopes of the craters, unless the contrast stretching is doing something weird, as I'm to understand that the actual colors here are dark and darker.

FYI, the quality of the latest image released here:

http://solarsystem.nasa.gov/news/display.cfm?News_ID=49244

is higher than the one released at the NASA Photojournal. A comparison:

Click to view attachment

NASA 'Solar System Exploration' left, NASA Photojournal right.

(I already compared the two versions of the bright-spot-close-up photo, but no dice.)

I remember posting in a Mercury dicussion that cooling metal ingots form radial cracks at their centres as they solidfy. I can't imagine how that could happen with water ice but I mention it in case the radial cracks at the centre of this crater suggest a similar formation process to somebody.

Hot-crossed bun, like Venus and Titan...
http://www.nasa.gov/mission_pages/cassini/...a/pia16165.html

That area certainly has not been resurfaced anytime recently...

Andy

This feature resembles a filled crater:

Click to view attachment

It could be just a play of shadows.

I think I see at lease three small craters inside the crater. They look like depressions.

It doesn't mean anything for the whole body. Enceladus is a great example where there are large areas of craters. But, this region seems to be old.

With (presumedly) bi-cubic interpolation and a little sharpening, plus rotation of 180 degrees to simplify perception, I'm getting a good quality directly from PIA19065.tif:
Click to view attachment
But now as I'm going too see things like this it's time for me to have a break.

So glad the JPG vs. TIF thing at the Photojournal has been resolved.


I had the same thought. I can see a Cyclus americanus (Mazon Creek), or perhaps a tick.

The crust of Ceres seems to have a lot of fissures into which material slumps, leaving an excess of crater-like pits. That's what I think caused that horizontal band of small craters on the floor of the big crater in the latest image, and grooves on part of the rim.

The cause became clear last week when I noticed a multitude of pits in the plain south of spot 5 (lower left corner of PIA19560) are aligned in closely-spaced rows, revealing the location of dozens of fractures criss-crossing the region.

They seem to be associated with crack-like features radiating from the large (poorly imaged) southern basin:

Click to view attachment

I think what I am seeing is a dome like extension. What I am imagining (though have never heard of such a case) a plume jutting up through the crust to form the dome and the brittle rock layer deposited in the surrounding large crater, cracking in a tensile failure as the dome extends through the crust. Reasoning here is that this fault line seems to curve nicely around this formation and it almost seems there was another fault line starting just to the right of the top-left visible line.

Could also be a strange (off)center point in the crater and the floor cooled rapidly and buckled? Just throwing out crazy ideas; please ignore.

A stretch of the latest image shows well the albedo variations:
Click to view attachment

I like how the low-resolution rendition (thumbnail) of the latest released RC3 image looks a lot like the OpNav images that were taken on approach to Ceres. Also, what is that (apparently) huge thing to the lower right? Is it a double crater, or is it just an awkward angle? It looks kind of bilobate.

It's an impact basin, but so far, it's been tricky to interpret. There appears to be topographic (tectonic?) variations on the floor similar to those in the equatorial 'sand dollar' basin, along with terrain modification ('valleying' and whatever else) of the rim. Oh, and albedo variations. No wonder the initial approach images were so confusing.

Cannot take my eyes off latest DAWN image release and fredk's stretch. Here we have a body with a density of 2 and one that has never gone through the tidal processing that some of the outer planet moons with similar densities have experienced.

THIS IS SO COOL. If Ceres did not exist, theorists would have had to invent it as a starting point.

Big thank you to DAWN team for these image releases. And I have to second jgoldader praise several posts back on the incredible expertise of the personnel on unmannedspaceflight. Blow my mind every day.

Okay, back to lurking.

Craig

Today's release vs. January:

Click to view attachment

I have to say that this is the "WOW" image for Ceres that I've been waiting for.

I can undertand recently exposed ice on Ceres being active in the sense that as it sublimes it may carry other materials upward in a comet-like fashion. I have one worrry and one question. The worry first: The primary reason for the exposure of the ice may not be evident even at high resolution. Whether venting due to some internal process or impact cratering is responsible there may have been subsequent processes such as scarp retreat that erase the tell-tale clues.

The question: Why would a plume of material from Ceres deposit dirt preferentially in one direction?

Direction of Ceres rotation would be one reason. The floating material which would then fall at different location depending upon the length of time each piece was aloft as Ceres rotated beneath it.

Andy

As we've been pondering bright spots, I've wondered about this dark crater (circled) just south of bright area #5.

Click to view attachment

To me it looks like the dark material has filled-in this crater leaving just a central peak. I've been looking for other images of that location that are higher resolution but nothing yet.

Andy

It's simply grote in the camera. You see it in different places on Ceres in different images.

Also, the vent (or vents) could be oriented in a certain direction. In the airless environment, the ejecta would follow a ballistic trajectory.

This would make the most sense to me as well, especially if such a vent was present in a fault zone.

Yet another stretch of pia19562.tif, cropped and magnified twice:
Click to view attachment
It shows, besides some texturing due to temporary jpg compression, brightness variations with some analogy to "the" bright spot, but with the advantage, that it's on a larger scale, hence better resolved.
Particularly along the south-western rim of the basin there seem to be parallel structures, which resemble pretty much terraces of some exposed strata.

No. The plume particles would share the same angular velocity as Ceres. If you jump in the air, the Earth doesn't rotate beneath you!

Here's a (somewhat reduced resolution) excerpt from an updated map I'm working on that shows this basin on the right side. It's mainly a mix of two images with a crescent view in the south and the favorite new low phase angle view (PIA19562) on the north.

Click to view attachment

The wandering depression (or set of crater chains and/or extra small crater rims?) off to the NNE side of the basin has a somewhat sinuous appearance. Here is another way to compare images - click below for a blinking animation.

Click to view attachment

That's correct, for a very local eruption. As the plume gets larger, the Coriolis force will become important. The Coriolis force will cause a radial plume to pick up some rotation relative to Ceres, at least at higher latitudes. Especially near the equator, there will also be a vertical component to the Coriolis force (for approximately horizontal-directed plume components), which will be opposite for eastward and westward directed plume components. Also the vertical-directed part of the plume will be deflected westward. So it's conceivable that this could cause an east-west asymmetry.

My guess is that the dark deposit (if that's what it is) east of region 5 is much too close to the source for the Coriolis effects to produce such a large asymmetry.

Sigh. The reason I didn't mention Coriolis forces is because they're likely to be negligible (as you agree). A simple calculation of the Rossby number shows that inertial forces in any supposed plume (which, I might add, I don't think is an explanation for anything on Ceres) will dominate over Coriolis forces.

The Coriolis parameter, f = 2(ω).sin(φ), where ω = 1.9234x10^-4 rad s^-1 and φ is the latitude.

For a plume at mid-latitudes (φ = 45°) involving particles erupted at, say, 250 m s^-1 over a length scale that appears from the images to be around 100 km, then the Rossby number is ~ 10
For Coriolis forces to become marginally important on these length scales, the eruption velocities would need to be nearer 30 m ^-1 (about 70 mph).

It's worth adding that ballistic emplacement over a maximum distance of 100 km in a gravity field of 0.27 m s^-2 requires a muzzle velocity of about 165 m s^-1 (and yes, I'm assuming planetary curvature is insignificant).

But (hopefully) Earth's surface is not in a vacuum. I was assuming we were discussing an impact. An impact would not have the same angular velocity as Ceres. But instead would impact, with dust/debris scattering and the body rotating underneath.

If you were to be thrown into Ceres, your remains would scatter with Ceres rotating underneath your remains while they were "airborne" (vacuum-borne).

"The plume particles would share the same angular velocity as Ceres. If you jump in the air, the Earth doesn't rotate beneath you!"

Not so sure about this. The Earth analogy is bad because you are not in the air long enough to see what happens. As for angular velocity, I think a particle or a high jumper would have the instantaneous linear velocity imparted by the rotation of Ceres, not angular velocity, but what happens to the plume would need some careful modelling.

Phil

It was a joke. I guess I won't include that in my next stand-up routine. When some contributors are doing mineralogy by colour or attempting geological interpretations of imaging artefacts, then if the worst I'm doing is making bad analogies... I'll live.

Secondly, I was under the impression that a 'volcanic' plume was being discussed rather than an impact plume.

Sorry I bothered to speak

They are beginning to showcase the southern hemisphere:

http://photojournal.jpl.nasa.gov/catalog/PIA19554

FYI, the image is flipped horizontally. Here it is restored

Click to view attachment

(Edit: TIF converted to JPG.) :

Agreed. Once the particles separated from the larger body they would move with independent vectors consisting of the linear velocity at the time of separation, the force of gravity between the the particle and the parent body, and the acceleration from the separation event. The sum of those vectors should produce ballistic trajectories.